Three-dimensional evaluation of the association between face and back asymmetry among pre-pubertal subjects.

Abstract

The aim was to compare the degree of back symmetry in two groups of subjects with and without pathologic facial asymmetry and to assess any possible associations between face and back asymmetry evaluated on three-dimensional surface face and back scans. The study design consisted of allocation of 70 subjects (35 females, 35 males) aged 6.4±0.5 years, according to the percentage of whole face symmetry assessed on three-dimensional (3D) facial scans into a 'symmetric' (symG; symmetry ≥70%) and 'asymmetric'(asymG; symmetry <70%). The 3D face and back scans were analysed using colour deviation maps and percentages of symmetry of the whole face and back surfaces as well as their three separate areas: forehead, maxillary and mandibular areas for the face and neck, upper and middle trunk areas for the back, were calculated. Non-parametric statistical tests were used for between-group comparisons (Mann-Whitney U test). Within each group, differences between each face or back area were tested with the Friedman test. Correlations between face and back symmetry were assessed with the Spearman rho coefficient. The symG exhibited a significantly higher symmetry in each facial area than the asymG. The mandibular area was the least symmetric area of the face within each group, with significantly smaller values than the maxillary area in the symG and significantly smaller values than the forehead and maxillary area in the asymG. The percentage of whole back symmetry did not significantly differ (p>0.05) between the symG ( 82.00% [67.4;88.00]) and asymG (74.3% [66.1;79.6]). The only significant between-group difference was observed for the symmetry of the upper trunk area (p=0.021), with lower symmetry values in the asymG. No significant associations were detected between face and back parameters. The percentages of symmetry in each facial area were significantly higher among subjects without pathologic facial asymmetry. The most asymmetric area of the face, regardless of the degree of whole face symmetry, was its mandibular area. No significant differences were detected within different back areas; however, subjects with asymmetric faces showed significantly smaller symmetry of their upper trunk area.